arXiv subjects

Yujie Lian

Publications and source records attributed to Yujie Lian.

29 records · Page 2Linked to original sources

arXiv2021

Consistency testing for invariance of the speed of light at different redshifts: the newest results from strong lensing and type Ia supernovae observations

The invariance of the speed of light in the distant universe has profound significance for fundamental physics. In this paper, we propose a new model-independent method to test the invariance of the speed of light $c$ at different redshifts by combining the strong gravitational lensing (SGL) systems and the observations of type-Ia supernovae (SNe Ia). All the quantities used to test the deviation of $c$ come from the direct observations, and the absolute magnitudes of SNe Ia need not to be calibrated. Our results show that the speed of light in the distant universe is no obvious deviation from the constant value $c_0$ within the uncertainty based on current observations. Moreover, we conclude that the currently compiled SGL and SNe Ia Pantheon samples may achieve much higher precision $Δc/c\sim10^{-2}$ for the deviation of $c$ than all previously considered approaches. The forthcoming data from the Legacy Survey of Space and Time and Wide-Field InfraRed Space Telescope will achieve more stringent testing for deviation of the SOL (at the level of $Δc/c \sim10^{-3}$) by using our model-independent method. Finally, we discuss the potential ways in which our technique might be improved, focusing on the treatment of possible sources of systematic uncertainties.

astro-ph.CO↗

arXiv2021

Probing modified gravity theories with multiple measurements of high-redshift quasars

In this paper, we quantify the ability of multiple measurements of high-redshift quasars (QSOs) to constrain several theories of modified gravity, including the Dvali-Gabadadze-Porrati braneworld scenario, generalized Chaplygin gas, $f(T)$ modified gravity, and Modified Polytropic Cardassian model. Recently released sample of 1598 quasars with X-ray and UV flux measurements in the redshift range of $0.036\leq z \leq 5.1003$, as well as a compilation of 120 intermediate-luminosity radio quasars covering the redshift of $0.46 < z < 2.76$ are respectively used as standard probes at higher redshifts. For all considered modified gravity theories, our results show that there is still some possibility that the standard $Λ$CDM scenario might not be the best cosmological model preferred by the current quasar observations. In order to improve cosmological constraints, the quasar data are also combined with the latest observations of baryon acoustic oscillations (BAO), which strongly complement the constraints. Finally, we discuss the support given by the data to modified gravity theories, applying different information theoretic techniques like the Akaike Information Criterion (AIC), Bayesian Information Criterion (BIC) and Jensen-Shannon divergence (JSD).

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arXiv2021

The velocity dispersion function of early-type galaxies and its redshift evolution: the newest results from lens redshift test

The redshift distribution of galactic-scale lensing systems provides a laboratory to probe the velocity dispersion function (VDF) of early-type galaxies (ETGs) and measure the evolution of early-type galaxies at redshift z ~ 1. Through the statistical analysis of the currently largest sample of early-type galaxy gravitational lenses, we conclude that the VDF inferred solely from strong lensing systems is well consistent with the measurements of SDSS DR5 data in the local universe. In particular, our results strongly indicate a decline in the number density of lenses by a factor of two and a 20% increase in the characteristic velocity dispersion for the early-type galaxy population at z ~ 1. Such VDF evolution is in perfect agreement with the $Λ$CDM paradigm (i.e., the hierarchical build-up of mass structures over cosmic time) and different from "stellar mass-downsizing" evolutions obtained by many galaxy surveys. Meanwhile, we also quantitatively discuss the evolution of the VDF shape in a more complex evolution model, which reveals its strong correlation with that of the number density and velocity dispersion of early-type galaxies. Finally, we evaluate if future missions such as LSST can be sensitive enough to place the most stringent constraints on the redshift evolution of early-type galaxies, based on the redshift distribution of available gravitational lenses.

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arXiv2020

Model-independent constraints on cosmic curvature: implication from the future gravitational wave observation DECIGO

A model-independent test of the cosmic curvature parameter $Ω_k$ is very important in cosmology. In order to estimate cosmic curvature from cosmological probes like standard candles, one has to be able to measure the luminosity distance $D_L(z)$, it's derivative with respect to redshift $D'_L(z)$ and independently know the expansion rate $H(z)$ at the same redshift. In this paper, we study how such an idea could be implemented with the future generation of space-based DECi-hertz Interferometer Gravitational-wave Observatory (DECIGO), in combination with cosmic chronometers providing cosmology-independent $H(z)$ data. Our results show that for the Hubble diagram of simulated DECIGO data acting as a new type of standard siren, it would be able to constrain cosmic curvature with the precision of $ΔΩ_k= 0.09$ with the currently available sample of 31 measurements of Hubble parameters. In the framework of the third generation ground-based gravitational wave detectors, the spatial curvature is constrained to be $ΔΩ_k= 0.13$ for Einstein Telescope (ET). More interestingly, compared to other approaches aiming for model-independent estimations of spatial curvature, our analysis also achieves the reconstruction of the evolution of $Ω_k(z)$, in the framework of a model-independent method of Gaussian processes (GP) without assuming a specific form. Therefore, one can expect that the newly emerged gravitational wave astronomy can become useful in local measurements of cosmic curvature using distant sources.

astro-ph.CO↗

arXiv2020

A model-independent constraint on the Hubble constant with gravitational waves from the Einstein Telescope

In this paper, we investigate the expected constraints on the Hubble constant from the gravitational-wave standard sirens, in a cosmological-model-independent way. In the framework of the well-known Hubble law, the GW signal from each detected binary merger in the local universe ($z<0.10$) provides a measurement of luminosity distance $D_L$ and thus the Hubble constant $H_0$. Focusing on the simulated data of gravitational waves from the third-generation gravitational wave detector (the Einstein Telescope, ET), combined with the redshifts determined from electromagnetic counter parts and host galaxies, one can expect the Hubble constant to be constrained at the precision of $\sim 10^{-2}$ with 20 well-observed binary neutron star (BNS) mergers. Additional standard-siren measurements from other types of future gravitational-wave sources (NS-BH and BBH) will provide more precision constraints of this important cosmological parameter. Therefore, we obtain that future measurements of the luminosity distances of gravitational waves sources will be much more competitive than the current analysis, which makes it expectable more vigorous and convincing constraints on the Hubble constant in a cosmological-model-independent way.

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arXiv2020

Model-independent constraints on cosmic curvature: implication from updated Hubble diagram of high-redshift standard candles

The cosmic curvature ($Ω_k$) is a fundamental parameter for cosmology. In this paper, we propose an improved model-independent method to constrain the cosmic curvature, which is geometrically related to the Hubble parameter $H(z)$ and luminosity distance $D_L(z)$. Using the currently largest $H(z)$ sample from the well-known cosmic chronometers, as well as the luminosity distance $D_L(z)$ from the relation between the UV and X-ray luminosities of 1598 quasars and the newly-compiled Pantheon sample including 1048 SNe Ia, 31 independent measurements of the cosmic curvature $Ω_k(z)$ can be expected covering the redshift range of $0.07<z<2$. Our estimation of $Ω_k(z)$ is fully compatible with flat Universe at the current level of observational precision. Meanwhile, we find that, for the Hubble diagram of 1598 quasars as a new type of standard candle, the spatial curvature is constrained to be $Ω_k=0.08\pm0.31$. For the latest Pantheon sample of SNe Ia observations, we obtain $Ω_k= -0.02\pm0.14$. Compared to other approaches aiming for model-independent estimations of spatial curvature, our analysis also achieves constraints with competitive precision. More interestingly, it is suggested that the reconstructed curvature $Ω_k$ is negative in the high redshift region, which is also consistent with the results from the model-dependent constraints in the literature. Such findings are confirmed by our reconstructed evolution of $Ω_k(z)$, in the framework of a model-independent method of Gaussian processes (GP) without assuming a specific form.

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arXiv2020

Testing the cosmic opacity at higher redshifts: implication from quasars with available UV and X-ray observations

In this paper, we present a cosmological model-independent test for the cosmic opacity at high redshifts ($z\sim5$). We achieve this with the opacity-dependent luminosity distances derived from nonlinear relation between X-ray and UV emissions of quasars, combined with two types of opacity-independent luminosity distances derived from the Hubble parameter measurements and simulated gravitational wave (GW) events achievable with the Einstein Telescope (ET). In the framework of two phenomenological parameterizations adopted to describe cosmic opacity at high redshifts, our main results show that a transparent universe is supported by the current observational data at 2$σ$ confidence level. However, the derived value of the cosmic opacity is slightly sensitive to the parametrization of $τ(z)$, which highlights the importance of choosing a reliable parametrization to describe the optical depth $τ(z)$ in the early universe. Compared with the previous works, the combination of the quasar data and the $H(z)$/GW observations in similar redshift ranges provides a novel way to confirm a transparent universe ($ε=0$ at higher redshifts $z\sim 5$), with an accuracy of $Δε\sim 10^{-2}$. More importantly, our findings indicate that a strong degeneracy between the cosmic opacity parameter and the parameters characterizing the $L_{UV}-L_X$ relation of quasars, which reinforces the necessity of proper calibration for such new type of high-redshift standard candle (in a cosmological model-independent way).

astro-ph.CO↗

arXiv2020

Testing the cosmic curvature at high redshifts: the combination of LSST strong lensing systems and quasars as new standard candles

The cosmic curvature, a fundamental parameter for cosmology could hold deep clues to inflation and cosmic origins. We propose an improved model-independent method to constrain the cosmic curvature by combining the constructed Hubble diagram of high-redshift quasars with galactic-scale strong lensing systems expected to be seen by the forthcoming LSST survey. More specifically, the most recent quasar data are used as a new type of standard candles in the range $0.036<z<5.100$, whose luminosity distances can be directly derived from the non-linear relation between X-ray and UV luminosities. Compared with other methods, the proposed one involving the quasar data achieves constraints with higher precision ($ΔΩ_k\sim 10^{-2}$) at high redshifts ($z\sim 5.0$). We also investigate the influence of lens mass distribution in the framework of three types of lens models extensively used in strong lensing studies (SIS model, power-law spherical model, and extended power-law lens model), finding the strong correlation between the cosmic curvature and the lens model parameters. When the power-law mass density profile is assumed, the most stringent constraint on the cosmic curvature $Ω_k$ can be obtained. Therefore, the issue of mass density profile in the early-type galaxies is still a critical one that needs to be investigated further.

astro-ph.CO↗

arXiv2020

Quantum fluctuation of entanglement for accelerated two-level detectors

Quantum entanglement as the one of the most general quantum resources, can be quantified by von Neumann entropy. However, as we know, the von Neumann entropy is only statistical quantity or operator, it therefore has fluctuation. The quantum fluctuation of entanglement (QFE) between Unruh-Dewitt detector modeled by a two-level atom is investigated in a relativistic setting. The Unruh radiation and quantum fluctuation effects affect the precise measurement of quantum entanglement. Inspired by this we present how the relativistic motion effects QFE for two entangled Unruh-Dewitt detectors when one of them is accelerated and interacts with the neighbor external scalar field. We find that QFE first increases by the Unruh thermal noise and then suddenly decays when the acceleration reaches at a considerably large value, which indicates that relativistic effect will lead to non-negligible QFE effect. We also find that the initial QFE (without acceleration effect) is minimum with the maximally entangled state. Moreover, although QFE has a huge decay when the acceleration is greater than $\sim0.96$, concurrence also decays to a very low value, the ratio $ΔE/C$ therefore still large. According to the equivalence principle, our findings could be in principle applied to dynamics of QFE under the influence of gravitation field.

quant-ph↗

arXiv2020

Model-independent constraints on Lorentz invariance violation: implication from updated Gamma-ray burst observations

Astrophysical observations provide a unique opportunity to test possible signatures of Lorentz Invariance Violation (LIV), due to the high energies and long distances involved. In quantum theory of gravity, one may expect the modification of the dispersion relation between energy and momentum for photons, which can be probed with the time-lag (the arrival time delay between light curves in different energy bands) of Gamma-ray bursts (GRBs). In this paper, by using the detailed time-delay measurements of GRB 160625B at different energy bands, as well as 23 time-delay GRBs covering the redshifts range of $z=0.168-2.5$ (which were measured at different energy channels from the light curves), we propose an improved model-independent method (based on the newly-compiled sample of $H(z)$ measurements) to probe the energy-dependent velocity due to the modified dispersion relation for photons. In the framework of a more complex and reasonable theoretical expression to describe the time delays, our results imply that the intrinsic time lags can be better described with more GRBs time delay data. More importantly, through direct fitting of the time-delay measurements of a sample of GRBs, our limit on the LIV energy scale is comparable to that with unknown constant for the intrinsic time lag, much lower than the Planck energy scale in both linear LIV and quadratic LIV cases.

astro-ph.CO↗

arXiv2019

Exploring the "$L$--$σ$" relation of HII galaxies and giant extragalactic HII regions acting as standard candles

Cosmological applications of HII galaxies (HIIGx) and giant extragalactic HII regions (GEHR) to construct the Hubble diagram at higher redshifts require knowledge of the "$L$--$σ$" relation of the standard candles used. In this paper, we study the properties of a large sample of 156 sources (25 high-$z$ HII galaxies, 107 local HII galaxies, and 24 giant extragalactic HII regions) compiled by Terlevich et al.(2015). Using the the cosmological distances reconstructed through two new cosmology-independent methods, we investigate the correlation between the H$β$ emission-line luminosity $L$ and ionized-gas velocity dispersion $σ$. The method is based on non-parametric reconstruction using the measurements of Hubble parameters from cosmic clocks, as well as the simulated data of gravitational waves from the third-generation gravitational wave detector (the Einstein Telescope, ET), which can be considered as standard sirens. Assuming the emission-line luminosity versus ionized gas velocity dispersion relation, $\log L ($H$β) = α\log σ($H$β)+κ$, we find the full sample provides a tight constraint on the correlation parameters. However, similar analysis done on three different sub-samples seems to support the scheme of treating HII galaxies and giant extragalactic HII regions with distinct strategies. Using the corrected "$L$--$σ$" relation for the HII observational sample beyond the current reach of Type Ia supernovae, we obtain a value of the matter density parameter, $Ω_{m}=0.314\pm0.054$ (calibrated with standard clocks) and $Ω_{m}=0.311\pm0.049$ (calibrated with standard sirens), in the spatially flat $Λ$CDM cosmology.

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